The discovery that there is a close relationship between ascorbate and glutathione dates from soon after the characterization of the chemical formulae of the two molecules ([Szent-Gyorgyi, 1931][1]; [Hopkins and Morgan, 1936][2]). Similarly, it has long been known that thylakoids can generate

Ascorbate and glutathione: the heart of the redox hub.

ROS signaling: the new wave?

Plants cannot survive without glutathione (γ-glutamylcysteinylglycine) or γ-glutamylcysteine-containing homologues. The reasons why this small molecule is indispensable are not fully understood, but it can be inferred that glutathione has functions in plant development that cannot be performed by other thiols or antioxidants. The known functions of glutathione include roles in biosynthetic pathways, detoxification, antioxidant biochemistry and redox homeostasis. Glutathione can interact in multiple ways with proteins through thiol-disulphide exchange and related processes. Its strategic position between oxidants such as reactive oxygen species and cellular reductants makes the glutathione system perfectly configured for signalling functions. Recent years have witnessed considerable progress in understanding glutathione synthesis, degradation and transport, particularly in relation to cellular redox homeostasis and related signalling under optimal and stress conditions. Here we outline the key recent advances and discuss how alterations in glutathione status, such as those observed during stress, may participate in signal transduction cascades. The discussion highlights some of the issues surrounding the regulation of glutathione contents, the control of glutathione redox potential, and how the functions of glutathione and other thiols are integrated to fine-tune photorespiratory and respiratory metabolism and to modulate phytohormone signalling pathways through appropriate modification of sensitive protein cysteine residues.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2011.02400.x

Glutathione in plants: an integrated overview.

Glutathione (GSH) is a tripeptide, which has many biological roles including protection against reactive oxygen and nitrogen species. The primary goal of this paper is to characterize the principal mechanisms of the protective role of GSH against reactive species and electrophiles. The ancillary goals are to provide up-to-date knowledge of GSH biosynthesis, hydrolysis, and utilization; intracellular compartmentalization and interorgan transfer; elimination of endogenously produced toxicants; involvement in metal homeostasis; glutathione-related enzymes and their regulation; glutathionylation of sulfhydryls. Individual sections are devoted to the relationships between GSH homeostasis and pathologies as well as to developed research tools and pharmacological approaches to manipulating GSH levels. Special attention is paid to compounds mainly of a natural origin (phytochemicals) which affect GSH-related processes. The paper provides starting points for development of novel tools and provides a hypothesis for investigation of the physiology and biochemistry of glutathione with a focus on human and animal health.

https://downloads.hindawi.com/archive/2012/736837.pdf

Glutathione Homeostasis and Functions: Potential Targets forMedical Interventions

Not just a circle: flux modes in the plant TCA cycle

The complex antioxidant network of plant and animal cells has the thiol tripeptide GSH at its centre to buffer ROS (reactive oxygen species) and facilitate cellular redox signalling which controls growth, development and defence GSH is found in nearly every compartment of the cell, including the nucleus Transport between the different intracellular compartments is pivotal to the regulation of cell proliferation GSH co-localizes with nuclear DNA at the early stages of proliferation in plant and animal cells Moreover, GSH recruitment and sequestration in the nucleus during the G1- and S-phases of the cell cycle has a profound impact on cellular redox homoeostasis and on gene expression For example, the abundance of transcripts encoding stress and defence proteins is decreased when GSH is sequestered in the nucleus The functions of GSHn (nuclear GSH) are considered in the present review in the context of whole-cell redox homoeostasis and signalling, as well as potential mechanisms for GSH transport into the nucleus We also discuss the possible role of GSHn as a regulator of nuclear proteins such as histones and PARP [poly(ADP-ribose) polymerase] that control genetic and epigenetic events In this way, a high level of GSH in the nucleus may not only have an immediate effect on gene expression patterns, but also contribute to how cells retain a memory of the cellular redox environment that is transferred through generations

A nuclear glutathione cycle within the cell cycle

Mitochondrial electron transport pathways exert effects on carbon-nitrogen (C/N) relationships. To examine whether mitochondria-N interactions also influence plant growth and development, we explored the responses of roots and shoots to external N supply in wild-type (WT) Nicotiana sylvestris and the cytoplasmic male sterile II (CMSII) mutant, which has a N-rich phenotype. Root architecture in N. sylvestris seedlings showed classic responses to nitrate and sucrose availability. In contrast, CMSII showed an altered 'nitrate-sensing' phenotype with decreased sensitivity to C and N metabolites. The WT growth phenotype was restored in CMSII seedling roots by high nitrate plus sugars and in shoots by gibberellic acid (GA). Genome-wide cDNA-amplified fragment length polymorphism (AFLP) analysis of leaves from mature plants revealed that only a small subset of transcripts was altered in CMSII. Tissue abscisic acid content was similar in CMSII and WT roots and shoots, and growth responses to zeatin were comparable. However, the abundance of key transcripts associated with GA synthesis was modified both by the availability of N and by the CMSII mutation. The CMSII mutant maintained a much higher shoot/root ratio at low N than WT, whereas no difference was observed at high N. Shoot/root ratios were strikingly correlated with root amines/nitrate ratios, values of <1 being characteristic of high N status. We propose a model in which the amine/nitrate ratio interacts with GA signalling and respiratory pathways to regulate the partitioning of biomass between shoots and roots.

/pdf/mitochondrial-respiratory-pathways-modulate-nitrate-sensing-g8wnqjxyh8.pdf

Tonja Wolff

Papers

A nuclear glutathione cycle within the cell cycle

Mitochondrial respiratory pathways modulate nitrate sensing and nitrogen-dependent regulation of plant architecture in Nicotiana sylvestris